2
698 Annotations DRUGS UNDER THE TONGUE TWENTY years ago Grossmann and Sandor 1 proved beyond question that nitroglycerin is freeely absorbed from the sublingual space. An official palatable tablet is provided for use in angina pectoris but it is still uncer- tain whether absorption is rapid enough to bring the drug into action before the attack subsides spontaneously. The later assumption that morphine can be adminis- tered with advantage by the same route has been based largely on analogy and perhaps hopeful thinking. Walton 2 has now shown by animal experiment and human controls that unless morphine which is placed under the tongue is subsequently swallowed an amount at least ten times as great as the subcutaneous dose is needed to produce’<jcomparable effects. For the relief of pain therefore, at least two grains would be required and this might prove dangerous if swallowed. Dihydro- morphinone (’Dilaudid ’)’and codeine proved equally ineffective sublingually. Diacetylmorphine (heroin made a better showing with a sublingual/subcutaneous effective dose ratio of five instead of ten to one, but this still seems outside the range of safe therapeutics. Drugs can be classified from this point of view into four groups. First, there are those sufficiently well absorbed in the mouth to be operative in reasonable dosage-e.g., nitroglycerin, apomorphine, cocaine and nicotine-even if some of them, such as ergotamine tartrate, are more effective when swallowed. In the second group are those which are well absorbed but only effective when given in doses which would be dangerous if ingested-e.g., morphine, strychnine, atropine and picrotoxin. Then there are some which though absorbed usefully are either irritant locally, such as pentobarbital, or too insoluble to go into solution in the small amount of fluid available. Last come a large group of drugs which fail to penetrate the mucous membrane or are only taken up at insigni- ficant rates, for example, leptazol, strophanthin, digoxin, ergometrine. The sublingual route may prove valuable for the administration of substances which are destroyed by the ordinary processes of digestion. Thus it has been reported s that in Addison’s disease adequate amounts of desoxycortone can be introduced in this manner over a considerable period, and posterior pituitary extract, in double the intramuscular dose, is sometimes given in the same way. Several testosterone compounds and cestro- gens are also usefully absorbed and so support Walton’s thesis that there is a close relationship between the lipoid solubility of a drug and its ability to pass the buccal mucous barrier. The correlation however is not suffici- ently close to remove the necessity of investigating the behaviour of each individual substance before relying on sublingual absorption. TOOTHACHE AND AVIATION APART from the emotional stresses to which the airman is subjected, three main physical strains are placed upon him-low temperature, low pressure and centrifugal force, the effect of the first two being in- creased by altitude and the third by tight turns or loops. The possibility of low temperature at high altitude causing dental pain has-been greatly overrated and some curious statements have been made, apparently through forgetting that the cheeks, lips, tongue and saliva all insulate the teeth against temperature changes. Thus Koelsch 4 has suggested that the cold is sufficient to make metal fillings contract and fall out. Other writers have suggested that amalgam fillings would disintegrate, perhaps having in mind the fact that 1. Grossmann, M. and Sandor, J. Klin. Wschr. 1923, 2, 1833. 2. Walton, R. P, J. Amer. med. Ass. 1944, 124, 138. 3. Anderson, E., Haymaker, W., Henderson, E. Ibid, 1940, 115, 2167. 4. Koelsch, F. Handbuch der Berufskrankheiten, Jena, 1935. tin, which may be used in small quantities in the amalgam, rapidly becomes amorphous at —48° C. The fallacy in these suggestions has been shown by HoCrvey.1 Using a thermocouple sealed into a tooth he has demon. c strated that when modern oxygen equipment is used the range of temperature- recorded is about 20-45° C., well within everyday limits. An iced drink- taken at ground level reduced the temperature of the tooth to 12° C., far lower than the lowest temperature recorded for altitude. The deleterious effects of low barometric pressure at great heights have largely been countered by the use of the pressure sealed cabin. At medium or high altitudes, if the flyer is exposed to the fall in pressure, there is no reason why the normal tooth should be affected more than any other organ. " Bends," due to the escape of nitrogen bubbles into the tissues, typically gives rise to joint and muscle pains, or more rarely to nervous signs, and though it may produce dental pain it is unlikely to do so without other symptoms. In a case of diver’s bends recorded by Donald 6 the patient had toothache as part of a severe temporary trigeminal neuralgia for which a bubble involving the second branch of the trigeminal nerve was blamed. It is of course pos- sible, in an improperly filled tooth with an air-space over the pulp under a sealed filling, that the change in volume with pressure might give rise to pain, and Restarski 7 has shown by staining methods with extracted teeth that leakage round the margin of a filling takes place more readily under gross changes in pressure if the filling materials are improperly mixed. In a turn or loop centrifugal force is usually acting from head to feet. This is a well-known cause of " blackout " but is unlikely to cause dental pain. A tooth with a slight degree of pulpitis might be made to ache by the increased blood content in the narrow pulp chamber when the centrifugal force acted in the opposite direction, but an aircraft is seldom manoeuvred in such a manner. It will be seen then that none of the three main conditions peculiar to flying are likely to give rise to pain in sound teeth. Where however a pathological state already exists, known or unsuspected, flying conditions may exacer- bate it, and so draw attention to it. Regular dental inspections and X rays are clearly an important part of the periodical examination of flying personnel, and the rarity of toothache in pilots and air crews on flying duties is a tribute to the efficiency of the RAF dental service. DUST IN FOUNDRIES WORKERS in steel foundries, and to a less extent in other foundries, are exposed to the risk of silicosis from inhalation of dust when moulding sand is being cleaned off the metal castings. War has brought with it more casting, more dust, and more risk. Silieosis became a matter of concern in America in the late ’twenties, some 15 years after the increase of foundry activity which began in 1915-1916. A similar increase could no doubt be shown in other steel-producing countries and it is to be anticipated after this war unless active measures are taken to control foundry dust. These and other points are made 8 by Ross and Shaw from their observa- tions in 1942 of conditions in 28 foundries in three Australian States. From 15 foundries they took samples for counting and chemical analyses to determine the dust concentration and type of dust to which the workers were exposed-using the Owens dust counter and the Greenburg-Smith impinger. For their purpose the thermal precipitator was found less suitable.. Their results embody a prodigious amount of tedious but useful work. Their method too of calculating and com- 5. Harvey, W. Brit. dent. J. 1943, 75, 221. 6. Donald, K. W. Brit. med. J. 1944, i, 590. 7. Restarski, J. S. Nav. med. Bull. Wash. 1944, 42, 155. 8. Ross, A. A. and Shaw, N. H. Dust Hazards in Australian Foundries. Technical report No. 1, Industrial Welfare Division, Department of Labour and National Service, Com- monwealth of Australia, 1943.
